Automatic sound picture dubbing system



Feb.` 4, 1ML H, sul-{ELLER ETAL 2,230,949

AUTOMATIC SOUND PICTURE DUBBING SYSTEM Original Filed Jan. 18, 19.37Sheecs-Shee'I l AUTOMATIC SOUND PICTURE DUBBING SYSTEM Original FiledJan. 18, 1937 2 Sheets-Sheet 2 MST @Sv s kl I Patented Feb. il, 1941uNrrsEo srA'rEs AUTOMATIC .SOUND PICTURE DUBBING SYSTEM Herman S.Heller, West Los Angeles, and Frank M. Kennedy, Los Angeles, Calif.;said Kennedy assigner to said Heller Application January 18, 1937,Serial No. 121,100 Renewed July 1, 1940 11 Claims.

This invention relates generally to the art of dubbing motion picturesound records, and deals more particularly with automatic dubbingsystems for motion picture sound records.

The expression dubbing as applied to sound pictures contemplates threevarieties of operations, namely, scoring, or adding incidental music toan existing sound record, synchronizing, or adding background soundeffects at appropriate places in the originally taken sound record, andsimple re-recording, that is, recording an original record for instanceat a dilierent volume level, or with desired volume modifications.rlhese three classes of dubbing operations may of course be performedsingly or in combination.

In practice, an original or existing sound record is run synchronouslywith a sound record or records having the incidental music or soundeieots to be dubbed in, the electrical sound currents reproduced fromsuch component records, are mixed at the desired volume levels by amixer, and the resulting composite electrical sound current is recordedon the new record. An operator, called a mixer, operates a series ofvolume change devices or faders controlling the relative amplitudes ofthe several electrical sound currents combined Within the mixer. Thisoperator is furnished with a loud speaker or monitoring horn from whichthe resultant composite electrical sound current is audibly reproducedsimultaneously with recording on the new record, and by listening tothis reproduction and simultaneously operating his controls, the mixerattempts to control the amplitudes of the several input currents in suchmanner as to combine lthem at proper relative amplitudes to produce thedesired combination sound record. If a mistake in judgment is made, anda sound is recorded at too high or too low volume, the whole operationmust be performed over again. The Work is highly tedious, and is inreality impossible to complete to satisfaction. Many retakes are made,with. a resultant wattage of iilm, and the iinal product .is invariablyno more than a rough compromise with the actual result Wanted.

t is the object of the present invention to provide an automatic dubbingsystem, enabling the desired volume levels or changes to be individuallypredetermined for each component or dummy record before any recording onlm is done, after which the component records may be run simultaneouslyand their output mixed and recorded under automatic mixer control.

The system in one aspect may be considered as a pantograph, wherein aseries of executed motions of the fader may be repeated or reproduced atany time in the future. In other Words, the system of the presentinvention reproduces automatically the movements of the mixer made Whilehe is manipulating his mixing or volume controls, but this reproductionis accomplished at any desired time in the future. This reproduction infact is a play back of the original movements of the mixing or volumecontrol members which, thereby, causes the same degree of volume controlas the operator or mixer originally effected. In other words, the playback is an accurate replica of the original movement of the mixing orvolume control settings.

The invention in all its aspects, including its various objects andcorresponding accomplishments, will be best understood Without furtherpreliminary discussion by referring now to the following detaileddescription of a present illustrative embodiment thereof, referencebeing had to the accompanying drawings, in which:

Fig. 1 is a schematic diagram showing a typical dubbing system; and

Fig. 2 is a schematic diagram of an illustrative automatic control unitin accordance with the present invention, it being understood that themixer unit indicated in Fig. 1 is to be provided with one such controlunit as is shown in Fig. 2 for each component record of the completedubbing system.

Reference is rst directed to Fig. 1, showing a typical dubbing or1re-recording system. A plurality of sound records l0, here indicated asof the motion picture film type, are indicated as 5 synchronously drivenby synchronous motors ll fed from a common three Wire distributingsystem l2. The records IG may contain different sounds to be combined onthe final film; for instance, one may contain the original talkingrecord, another may bear incidental music, another sound eiects, such asthe `sound. of a closing door, a pistol shot, etc. These several recordsare of course so prepared and driven as to synchronize with one another.The synchronizing system here indicated, comprising motors ll anddistributing system l2, may be of a type well known inthe art, it beingunderstood that each motor Il connected across distributing system I2will run in exact synohronism With each other such motor so connected. f

Optical and photo-electric means for producing electrical sound currentsfrom the records contained on films l 0 are diagrammatically indicatedat l5, and the electrical circuits which conduct 55 such sound currentto the mixing unit are indicated at I6.

Circuits I6 are connected into a mixer I1, which as heretofore knownycomprises a system for combining the electrical sound currents carriedby the several input circuits into a single output circuit, togetherwith individual manually controllable resistors, known as faders, forregulating the amplitudes, and therefore the Volume levelcharacteristics, of the input currents received from circuits I6.'I'hese resistors,'which are of well known type and need not beillustrated in Fig. l, thus serve to regulate the volume levelcharacteristics of each input sound current, and after such regulation,the several currents are combined in a conventional manner within themixer and are delivered to a common output circuit I8.

Output circuit I8 is shown as going to amplier I 9, and the output ofamplifier I0 is conducted by way of circuit 20 to an electro-opticalrecording means at ZI which records the composite electrical soundcurrent on final film 22. This final film 22 is indicated as driven by asynchronous motor 23 also connected across distributor system I2.

A monitor horn 25 enabling the operator controlling mixer I 'I to hearthe result of the volume changes which he imposes is indicated asconnected via circuit 26 to amplifier output circuit 20.

It will be understood that, in accordance with prior practice, the mixeroperator maintains a constant manual control over the faders controllingthe amplitudes of the several component sound currents which arecombined within the mixer and delivered to the single output circuitgoing to the final recorder. It will also be understood that in theevent this operator should make a mistake in judgment as to the volumeat which one sound current should be mixed with the others, that mistakewill not show up until the new record 22 has been developed, a printtaken therefrom and that print reproduced.

The present invention provides means whereby the successive positionsand changes of positions of each mixer fader during the manuallycontrolled run may later be automatically reproduced.

Fig. 2 shows one of the input circuits I6, which will be understood tocarry the electrical sound current produced by reproduction of one ofthe lms I0, and shows said circuit IS going to the terminals of a fader30 of conventional type. The fader is shown provided with the usualcontrol arm 3l adapted to wipe over fader contacts 32, and the outputcircuit 34 leading from the fader is connected as usual across one sideof input circuit IE and fader arm 3I. It will be understood withoutfurther description how resistor or fader 30 controls the amplitude ofthe electrical sound current carried by circuit 34 leading from thefader in accordance with the setting of fader arm 3l on contacts 32. ItWill be understood that the fader and its connections may be of anysuitable or conventional nature, so long as its operation controls theattenuation of the sound current delivered to circuits 34 and I8.

It is to be understood that there is one fader, such as 30, controllingeach input circuit I6, and a unit or system such as shown in Fig. 2 forautomatic control of each such fader 30. It will also be understood thatthe circuit 34 leading from each fader 30 is so connected within themixer to the corresponding circuits 34 leading from the other faders asto combine the several fader controlled sound currents within the singleoutput circuit represented at I3. Such mixer circuits are wellunderstood in the art and need not here be shown in detail, though inFig. 2 I conventionally indicate several fader circuits 34 as connectedinto a common input circuit I8 leading to amplifier I9.

The automatic control unit of Fig. 2 will now be considered in moredetail. Fader arm 3l is mounted on a manually rotatable shaft 40, whichalso carries the arms 400 and 40| of resistors 402 and 403,respectively. A low frequency oscillator 405 and a high frequencyoscillator 40B are provided, the frequencies of which may typically be50 cycles and 500 cycles, though it is to be understood that thisillustration constitutes no limitation on the invention. One terminal oflow frequency oscillator 405 is connected by lead 401 to the arm 400 ofresistor 402, and one terminal of high frequency oscillator 405 isconnected by lead 408' to arm 40| of resistor 403. The other terminalsof oscillators 405 and 406 are interconnected by a lead 409, which is inturn connected by lead 4m to a center tap on the primary winding 4II ofa transformer 4I2. Non-corresponding terminals of resistors 402 and 403are connected by leads 4I4 and 4I5, respectively, to the outsideterminals of transformer winding 4l I. That is, resistors 402 and 403are so connected that as resistor arms 400 and 40! rotate in the samedirection as shaft 40 is turned, the resistance in the circuit of oneoscillator is decreased as the resistance in the circuit of the otheroscillator is correspondingly or complementarily increased. Rotation offader shaft 40 therefore causes the low frequency oscillator currentinput to transformer winding 4II to increase as the high frequencyoscillator current input to said winding decreases, and vice versa, saidcurrents varying always complementarily to one another.

The secondary winding 4I8 of transformer 4I2 is connected to the inputterminals of an amplilier 4I9. The output terminals of amplifier 4I9 areconnected by leads 420 and 42| to stationary contacts 422 and 423,respectively, of a control switch 424. Movable switch arms 425 and 426are adapted to make with contacts 422 and 423, respectively, when movedtoward the left, as viewed in Fig. 2. Connected to these switch arms 425and 420 are circuit wires 42'! and 428 leading to a recording means,preferably of the magnetic tape type, and are here shown as going torecording and reproducing magnets 420.

The magnetic recording tape 430 passes between recording and reproducingmagnets 429 in the usual manner, the tape running from a supply reel 43|to a take-up reel 432, the latter being understood to be driven by asynchronous drive motor (not shown) powered from distributor system i 2,while the supply reel is adapted to be driven by any suitable re-windmotor (not shown).

It will be evident that, switch arms 425 and 426 being moved ove!` tothe left, the low and high frequency oscillator currents, which arecomplementarily varied as the fader shaft is rotated, are mixed withintransformer H2 and recorded together on tape 430.

The tape as here shown is provided with a separate erasing coil 434adapted to be energized by an alternating current supply circuit 435including a control switch 430. This circuit may be utilized to cleanall or a portion of the magnetic record oif the tape.

Switch arms 425 and 426 when moved to the right, as seen in Fig. 2, makewith stationary switch contacts 440 and 44|, which are connected acrossa circuit 442 leading to the input side of an amplifier 443. Thus, whentape 430 has been re-wound on reel 43|, and is again run forwardly toreel 432, the complementarily Varying (complementary amplitude)oscillator currents recorded on tape 430 are reproduced within coils429, and are amplied at 443. The output leads `444 and 445 of amplier443 are connected across a circuit `449, which interconnectscorresponding input terminals of a low-pass filter 441 and a high-passfilter 449. Low-pass filter 441 and high-pass filter 448 are thus bothfed from the output of amplifier 443. Low-pass filter 441 is designed topass substantially exclusively currents of a frequency corresponding tolow frequency oscillator 495 and high-pass filter 448 is designed topass substantially exclusively currents corresponding to high frequencyoscillator 496. Such low and high-pass filters are well known in theart,`and will require no explanation here.

Low-pass lter 441 is connected by leads 450 to the input winding 45| ofa transformer 452, while high-pass lter is connected by leads 453 to theinput winding 454 of a transformer 455.

The output of transformer 452 is amplified by a vacuum tube amplifier,generally designated at 459, and then rectified by a rectifierdesignated at 46|, while the output of transformer 455 is amplified by aVacuum tube amplifier indicated at 452, Vand then rectified by arectifier indicated at 453. As here shown, amplifiers 450 and 462 are ofthe push-pull type. Considering amplier 459 in detail, the secondarywinding 454 of transformer 452 is connected at its Vends through leads459 and 491 to the grid elements of two Vacuum tubes 459 and 459,respectively, while the center tap of transformer 454 is connected bylead 410 to the heater elements 419e of tubes 468 and 469, as indicated.Theplate leads 41| and 412 of tubes 458 and 459 are connected to the endterminals of the primary winding 413 of a transformer 414, while thecenter tap of winding 413 is connected by lead 415 to positive Bvoltage, as indicated.

Lead 419 includes a condenser 480, and connected to lead `479 betweensaid condenser and transformer winding 454 is one end of a resistanceelement 45|. The opposite end of resistance 48| is connected by wire 492with one end of a second resistance 483, the other end of which isconnected to lead 41,9 between condenser 480 and the heater elements oftubes 458 and 469. A condenser 494 is shunted across resistance483.

rIhe outside terminals of secondary winding 488 of transformer 414 areconnected by leads 489 and 499 to the plate elements 49| and 492 of apair ofrectifier tubes 493 and 494, respectively. 'I'hefilainentelements 495 and 496 of tubes 493 and 494 are connected in parallel, asindicated and connected across such filament elements is a resistanceelement 491, to the center of which is connected an output lead 498. Theother output lead 499 is connected tothe center tap of transformerwinding 488, as indicated.

It will be understood that the low frequency current passed by filter441 will be amplified by amplifier 469, and that the resulting amplifiedlow frequency current is rectified by tubes 493 .and 494, so thatoutputcircuit `498, 489 carries an amplied, rectified low frequency (50 cycle)current.

Amplifier 462 and rectifier 453 are the same as amplier 460 andrectier'46 I respectively, members of amplifier 452 and rectifier 453being identied with the saine reference characters as have been appliedto amplifier 430 and rectifier 46|, but with primes annexed.Accordingly, output circuit 498, 499 carries a rectified 50 cyclecurrent, while output circuit 499', 499' carries a rectified 500 cyclecurrent.

Output circuits 498, 499 and 498', 499 are provided with 1r net works50|] and 59|, respectively, each consisting of a pair of shunt connectedcondensers 502 and 593 and an intervening series connected inductance504. These net works or filters are designed to take out the 50 and 500cycle oscillation frequencies, passing only a uni-directional currentwave bounded by the complementary envelopes of the 50 and 500 cyclewaves received from the rectifiers, which envelopes will be understoodof course to be determined by the movements of resistor control arms 459and 49| during the making of record 430.

Circuits 498, 499 and 499', 499' are connected to a motor unit 5| 4.This unit, in the illustrative form here shown, comprises a .pair ofopposed series connected field windings 5H and 5I2, connected in serieswith leads 499 and 499, and a pair of series connected field windings5|3 and 5i4 connected in series with leads 498 and 499. As here shown,.the pairs of eld coils 5| |-5|2, and 5|3-5M are disposed at 90 from oneanother, all being radially disposed with reference to the axis ofrotation O of the motor armature. As here shown, adjacent coils 5|2 and5|4 are wound and connected so that their north poles are at their innerends, while coils 5H and 5|3 are so wound and connected that their southpoles are at their inner ends.

The motor armature A consists of a winding 529, wound to provide a northpole at one side of the armature and south pole at the other, asindicated. Opposite ends of the winding are connected yto direct currentsupply leads 524 and 525. The motor armature is normally positioned withits north pole side mid-way between the north poles at the inner ends ofcoils'5l2 and 5|4, and with its south pole side between the south polesat the inner ends of coils 5| I and 5|3.

It will be evident that the motor armature will tend to rotate in aclockwise direction under the inuence of the fields produced by coils5I2 and 5| and will tend to lrotate in a counter-clockwise directionunder the influence of the fields produced by coils 5|3 and 5|4. Thearmature will accordingly under all conditions seek and take a positiondependent upon the relative strengths of the currents flowing in saidtwo pairs of field coils.

The armature of motor 5|!) has a range of operation of something lessthan 90 of rotation; accordingly, since a rotation of as much as perhaps300 is desired to 'be imparted to the fader shaft, step-up gearingarrangements are ernployed. Thus, as here indicated, a gear 530 on motorshaft 523 drives a smaller gear 53| on a shaft 532.

Shaft 532 is adapted to be drivingly connected by magnetic clutch 533with fader shaft 40. The winding of magnetic clutch 533 is connected byleads 534 and 535 to the 4movable arm 536 and stationary contact 531,respectively, of control switch 424. Contact is made between said. arm536 and contact 531 when the switch is moved toward the right, to takeposition. A battery 538 is included in one of the leads leading tomagnetic clutch 533, as indicated.

The operation Kof the system may now be understood. It is assumed that aseries component 4sound record films I0 have been prepared, and that thespeech, sound effects, or music recorded on said films have been sosynchronized that when the several films are synchronously driven, thesounds recorded thereon may be reproduced in proper synchronous relationto one another. These lms I are then run in the system of Fig. 1, eachfilm being driven by its synchronous motor energized from the centraldistributing system I2. Switch 36 is open, so that nothing will berecorded at this time, switch 424 is moved to the left, to selectposition, and the magnetic recorder is operated so as to drive tape 430from supply reel 43| to take-up reel 432 in synchronous relation withthe drive of the sound films l0. The sound records on the several soundlms |0 are now all reproduced as electrical sound currents withincircuits I6, and these currents fiow by way .of fader controlledcircuits 34 and common mixer circuit I8 to amplifier I9, the output ofwhich is reproduced by monitor horn 25. 'I'he mixer operator listens tothe sound coming from the records |0 as reproduced by horn 25, and fromtime to time rotates the fader shafts 40 by means of knobs 39a, so as toadjust the fader `control arms 3| of the several faders 30 and therebychange the volume level of the several components of the reproducedsound as he may think desirable.

The rotation of each shaft 40 turns the corresponding arms 400 and 40|of resistors 402 and 403, respectively. As previously described,rotation of a fader shaft 40 in one direction increases the resistanceof one of the resistors 402 and 403 as it decreases the resistance atthe other, so that the amplitudes of the low frequency and highfrequency oscillation currents flowing from oscillators 405 and 406 aresimultaneously varied in opposite directions. That is, said currents arevaried complementarily to one another.

Switch arms 425 and 426 being moved to the left, or to select positionat this time, the two oscillator currents as thus complementarilycontrolled by resistors 402 and 403, are amplified at 4|9, and then fiowby way of switch 424 to recording coils 429, the two currents, both lowand high frequency, thus being recorded on magnetic tape 430.

At the end of the run, tape 430 is wound back from take-up reel 432 tosupply reel 43|, and switch 424 is shifted over to the right, to takeposition. Oscillators 405 and 406 are then out of the circuit, and coils429 are connected by way rof' switch 424 to input amplifier circuits442. Contact is also made between switch arm 536 and contact 531,energizing magnetic clutch 533, thus coupling motor shaft 523 with fadershaft 40.

The films I0 of Fig. l are run back to starting position, and film I0and tape 430 are then synchronously driven in a forward direction, carebeing taken that the films I0 and tape 430 start synchronously. The runnow to be made is simply -for the purpose of checking the correctness ofthe amplitude changes which were manually effected duringthe precedingrun, and recording switch 36 is therefore still left open at this time.

The high and low frequency complementarily varying current wavesrecorded on the tape 430 of each automatic unit are now reproducedwithin coils 429, are amplified at 443, and are divided at filters 441and 448, so that the low frequency current wave flows exclusively incircuit 459, and the high frequency current wave flows exclusively incircuit 453. These current waves are amplified at 460 and 462,respectively, are rectified at 46| and 463, respectively, and fiow incircuits 498, 499 and 498', 499 as complementarily varying directcurrent waves, the 50 and 500 cycle oscillator frequencies being removedat net works 500 and 50|. It will be evident that these current wavesrepresent the complementary resistance changes at resistors 402 and 403during the manual control run vof sound films I0.

'Ihese complementary varying currents then fiow in the opposed pairs ofmotor field coils 5|2 and 5| 3, 5| 4, so that the opposing rotativeforces on motor armature A likewise vary complementarily, with theresult that said armature shifts its position first one way and then theother from its mid position between said sets of eld coils. For eachpair of values of the complementary currents fiowing in the opposing eldcoils, there is a position at which the opposing forces on armature Aare in balance, and the armature therefore rotates back and forth underthe control of the complementary current waves.

This movement of motor armature A is transmitted by way of shaft 523 and532 and magnetic clutch 533 to fader shaft 40, the drive ratio at gears530 and 53| being such that the rotation of fader shaft 40 so receivedfrom the motor armature duplicates the original manually effectedrotations or movements of shaft 40 during the initial manuallycontrolled run of sound films I0.

It will now be evident that as sound films |0 are audibly reproduced byway of circuits I6, 34, |8, amplifier I9 and circuit 26, the volumelevel of reproduction of the several records will be controlled byfaders 30 under the automatic control of the records on the magnetictapes 430. The volume changes manually effected during the initialmanually controlled run may therefore be checked by the mixer before anyrecording on film is made. It will be evident that a single sound filmI0 may thus be reproduced and checked in the manner here described, or aplurality of such sound films |0 may be run together with their severalfaders all under individual automatic control and the composite effectnoted by listening to the reproduction from horn 25.

If a given sound is recorded at an undesirable volume level, thecorresponding section of the record on tape 430 may be modified. To dothis, the tape is rewound until the record portion to be modified isjust before erasing magnet 434. Switch 436 is then closed, and the taperun forwardly, the erasing current flowing in the magnet 434 erasing thepreviously made record on the tape. The tape is of course stopped whenthe section of the record to be modified has passed the magnet 434 andbeen erased. Switch 424 then being thrown to select position, and thetape having been rewound the proper distance, a

new position or set of positions of fader arm 3| may be recorded on thetape. Thus by this procedure the record on the tape may be modified inparts to correct earlier mistakes.

When the records on the tapes of all automatic fader control units aredeemed to be satisfactory, the recordation on nlm 22 may be made. Theseveral sound recordfiilms l0 are then to be synchronously driven withthe fresh negative nlm 22 on which the new composite sound record is tobe recorded. Switch 36 is closed, switch 424 of each automatic unit isagain in take position, and the magnetic tapes 430 having been rewoundand the films I0 and 22 all being at their starting positions, the mainswitch controlling the synchronous motor distributer system is closed.This run is carried out in the same way as the previously describedtrial run, except that theswitch 36 is closed and the final recording onnlm 22 is accordingly made. Thus the sound records on the several soundlms l0 are reproduced-as electrical sound currents Within circuits I6,and these currents flow by way of fader circuits 34, and common mixercircuit I8 to amplifier I9. The output current from the amplier flows torecording means 2l, producing a composite sound record on film 22. 'I'hesound current flowing in each mixer circuit 3d is controlled inamplitude by its corresponding fader 30, which in turn is under theautomatic control of the pre-estab-` lished fader-position recording ontape 43E). Thuseach component sound current going into mixer circuit I8is controlled in volume by its own automatic control unit in exactaccordance with the manual volume level adjustments which werepreviously made during the fselect run for the corresponding sound iilmIl), and which are represented on the fader-position record of thatautomatic control unit.

The automatic system thus duplicates each manual volume level adjustmentwhich was made during the select run, eliminating the possibility ofmistakes in judgment in effecting volume level changes in the nalrecording on film, and therefore eliminating entirely retakes on lm.

It will thus be understood that a record is made on the record element430 of each automaticunit of the manually eected movements of thevolumecontrol fader 30 of that unit during the manually controlled run ofsound films I0, and that in vsubsequent runs of lms IIJ, both for trialpurposes (withswitch 36 open), without recording on nlm, and in the nnalrun duringwhich a final recording is made on iilm22, said record 43)`produces electrical currents which control an electric motor devicedrivingly connected to the same volume control fader for automaticduplication of the manual volume adjustments made during the initial ormanually controlled run of sound lms I0.

We have now illustrated and described certain specific illustrativemeans for carrying our invention into effect; it is to be understood,however, that the disclosure given is for illustrative purposes only,and that various changes, modifications, and substitutions may be madeWithout departing from the spirit of our inventionlor of the appendedclaims.

We claim:

l. The herein described method, that comprises producing an electricalsound current-from an original sound record, audibly reproducing saidsound current, manually effecting desired amplitude modicatons in saidsound current by reference to such audible reproduction, making a recordof suchamplitude modifications, again producing an electrical soundcurrent from said original sound record, repeating the same amplitudemodifications in said electrical sound current under the control of saidamplitude modication record, and making a sound record of saidMamplitude modified electrical sound current.

2. The herein described method, that comprises producing an electricalsound current from an original sound record, audibly reproducing saidsound current, manually controlling the amplitude level of the soundcurrent as desired by reference` to such audible reproduction,simultaneously making a record of the manually effect- -ed controloperations, again producing an electrical sound current from saidoriginal sound record, effecting a control of the amplitude level ofsaid sound current by use an electrical current produced by simultaneousreproduction of said last mentioned record, and making a sound record ofsaid amplitude controlled sound current.

3. In a sound record dubbing system having a fader involving a movablemanually operable control member adapted to control the amplitude of anelectrical sound current, means for automatically controlling said fadercomprising means for recording manually effected movements of the fadercontrol member, and means controllable by the record so made forsubsequently automatically effecting similar movements of said fadercontrol member.

4. In a sound record dubbing system having a fader involving a movablemanually operable control member adapted to control the amplitude of anelectrical sound current, electric circuiting carrying two separatelycontrollable electric currents, means for complementarily varying saidcurrents in accordance with manually eiected operation of said fadercontrol member, means for recording said electric currents', means forsubsequently reproducing said electric currents from the records somade, and electromagnetic means controlled by said two currents foroperating the fader control member to reproduce the previously effectedmanual control operations of saidmember.

5. In a sound record dubbing system having a fader involving a movablemanually operable control .member adapted to control the amplitude of anelectrical `sound current, electric circuiting 4carrying two separatelycontrollable electric currents, means for complementarily varying saidcurrents in accordance with manually effected operation of said fadercontrol member, means for recording said electric currents, means forsubsequently reproducing said electric currents from the records somade, and electromagnetic means controlled by lsaid two currents foroperating the fader control member to duplicate the previously `effectedmanual control operations of said member, said electromagnetic meanscomprising a field winding adapted to carry one of said currents andanother field winding adapted to carry the other of said currents, saidwindings being disposed with the like magnetic poles in opposition toone another, a movable armature having a current carrying winding andarranged with one of its poles between and acted upon by said fieldwinding poles, and a coupling between said armature and the movablecontrol member of said fader.

.6. In a sound record dubbing system having a faderinvolving a movablemanually operable control member adapted to control the amplitude of anelectrical `sound current, electric circuiting carrying two separatelycontrollable electric currents,means for complementarily varying saidcurrents in Yaccordance with manually eiected operation of said fadercontrol member, means for recording said electric currents, means forsubsequently reproducing said electric currents from the records somade, and electromagnetic means controlled by said two currents foroperating the fader control member to duplicate ther previously effectedmanual control operations of said member, said electromagnetic meanscomprising a field winding adapted to carry one of said currents andanother field winding adapted to carry the other of said currents, saidwindings being disposed with like poles in opposition to one another, amovable armature having a magnetic pole between and acted upon by saidfield winding poles, and a coupling between said armature andl themovable control member of said fader.

7. In a sound record dubbing system having a A fader involving a movablemanually operable control member adapted to control the amplitude of anelectrical sound current, a pair of oscillators, one of higher frequencythan the other, electric circuiting carrying electric currents generatedby said oscillators, means for complementarily varying said oscillatorcurrents in accordance with manually effected operations of said fadercontrol member, means for recording said oscillator currents, means forsubsequently reproducing said currents, means for rectifying saidcurrents, and electromagnetic means controlled by the rectified currentsfor operating the fader control member in a manner to reproduce thepreviously effected manual lcontrol operations of said member.

8. In a sound record dubbing system having a fader involving a movablemanually operable control member adapted to control the amplitude of anelectrical sound current, a pair of oscillators, one of higher frequencythan the other, electric circuiting carrying electric currents generatedby said oscillators, means for complementarily varying said oscillatorcurrents in accordance with manually effected operations of said fadercontrol member, means for making a single record of said oscillatorcurrents, means for reproducing an electric current from said record, apair of filters for separating the current corresponding to the higherfrequency oscillator from' the current corresponding to the lowerfrequency oscillator, means for rectifying each of the resultingcurrents, and electromagnetic means controlled by the rectified currentsfor operating the fader control member in a manner to reproduce thepreviously effected manual control operations of said member.

9. In a sound record dubbing system having a fader involving a movablemanually operable control member adapted to control the amplitude of anelectrical sound current, a pair of oscillators, one of higher frequencythan the other, electric circuiting carrying electric currents generatedby said oscillators, means for complementarily varying said oscillatorcurrents in accordance with manually effected operations of said fadercontrolmember, means foi` making a single record of 'said oscillatorcurrents, means for reproducing an electric current from said record, apair of filters for separating the current corresponding to the higherfrequency oscillator from the current corresponding to the lowerfrequency oscillator, means for rectifying each of the resultingcurrents, means for filtering out the oscillator frequencies from therectified currents, thereby producing a pair of unidirectionalcomplementarily varying electric currents, and electromagnetic meanscontrolled by the last mentioned currents for operating thecomplementarily varying said oscillator currents in accordance withmanually effected operations of said fader control member, means formaking a single record of said oscillator currents, means Y, forreproducing an electric current from saidy record, a pair of filters forseparating the current correspondingrtothe higher frequency oscillatorfrom the current corresponding to the ilower frequency oscillator, meansfor rectifying each of the resulting currents, means for filtering outthe oscillator frequencies from the rectified currents, therebyproducing a pair of uni-directional complementarily varying electriccurrents, and electromagnetic means controlled by the last mentionedcurrents for operating the fader conf trol member to duplicate thepreviously effected manual control operations of said member, saidelectromagnetic means comprising a field winding adapted to carry one ofsaid rectified filtered currents and another -iield winding adapted tocarry the other of said rectified filtered currents, said windings beingdisposed with like poles in opposition to one another, a movablearmature having a current carrying winding and arranged with one of itspoles between and acted upon by said field winding poles, and a couplingbetween said armature and the movable control member of said fader.

1f1. In a sound record dubbing system having a fader involving a movablemanually operable control member adapted to control the amplitude of anelectrical sound current, a pair of oscillators, .one of higherfrequency than the other, electric circuiting carrying electric currentsgenerated by said oscillators, means for complementarily varying saidoscillator currents in accordance with manually effected operations ofsaid fader control Ymembenmeans for making a single record of saidoscillator currents, means for reproducing an electric current from saidrecord, a pair of filters forV separating the current corresponding tothe higher frequency oscillator from the current corresponding to thelower frequency oscillator, means for rectfying each of the resultingcurrents, means for filtering out the oscillator frequencies from therectified currents, thereby producing a pair of unidirectionalcomplementarily varying electric currents, and electromagnetic meanscontrolled by the last mentioned currents for operating the fadercontrol member to reproduce the previously effected manual controloperations of said member, said electromagnetic means comprising a fieldwinding adapted to carry one of said rectified filtered currents andanother field winding adapted to carry the other of said rectifiedfiltered currents, said windings being disposed with like poles inopposition to one another, a mov- -able armature having a magnetic polebetween and acted upon by said field winding poles, and a couplingbetween said armature and the movable control member of said fader.

HERMAN S. HELLER.

FRANK M. KENNEDY.

